1. FIELD OF THE INVENTION
This invention relates to a metallocene catalyst component for olefin polymerization, specifically, to a syndiospecific metallocene catalyst component having a polymerizable functional group substituent.
2. DESCRIPTION OF THE PRIOR ART
German patent application 2,608,863 discloses a catalyst system for the polymerization of ethylene consisting of bis(cyclopentadienyl)-titanium dialkyl, an aluminum trialkyl and water. German patent application 2,608,933 disclosed an ethylene polymerization catalyst system consisting of zirconium metallocenes of the general formula (cyclopentadienyl).sub.n Zr Y.sub.4-n, wherein Y represents R.sub.1 CH.sub.2 AlR.sub.2, CH.sub.3 CH.sub.2 AlR.sub.2 and CH.sub.3 CH (AlR.sub.2).sub.2 wherein R stands for an alkyl or metallo-alkyl, and n is a number within the range 1-4; and the metallocene catalyst is in combination with an aluminum trialkyl cocatalyst and water.
The use of metallocenes as catalysts in the copolymerization of ethylene and other alpha-olefins is also known in the art. U.S. Pat. No. 4,542,199 to Kaminsky, et al. disclosed a process for the polymerization of olefins and particularly for the preparation of polyethylene and copolymers of polyethylene and other alphaolefins. The disclosed catalyst system includes a catalyst of the formula (cyclopentadienyl).sub.2 MeRHal in which R is a halogen, a cyclopentadienyl or a C.sub.1 -C.sub.6 alkyl radical, Me is a transition metal, in particular zirconium, and Hal is a halogen, in particular chlorine. The catalyst system also includes an aluminoxane having the general formula Al.sub.2 OR.sub.4 (Al(R)--O).sub.n for a linear molecule and/or (Al(R)--O).sub.n+2 for a cyclic molecule in which n is a number from 4-20 and R is a methyl or ethyl moiety. A similar catalyst system is disclosed in U.S. Pat. No. 4,404,344.
U.S. Pat. No. 4,530,914 discloses a catalyst system for the polymerization of ethylene to polyethylene having a broad molecular weight distribution and especially a bimodal or multimodal molecular weight distribution. The catalyst system is comprised of at least two different metallocenes and an alumoxane. The patent discloses metallocenes that may have a bridge serving to make the rings stereorigid. The bridge is disclosed as being a C.sub.1 -C.sub.4 alkylene radical, a dialkyl germanium or silicon, or an alkyl phosphine or amine radical.
European patent Application 0185918 discloses a stereorigid, chiral metallocene catalyst for the polymerization of olefins. The bridge between the cyclopentadienyl groups is disclosed as being a linear hydrocarbon with 1-4 carbon atoms or a cyclical hydrocarbon with 3-6 carbon atoms. The application discloses zirconium as the transition metal used in the catalyst, and linear or cyclic alumoxane is used as a co-catalyst. It is disclosed that the system produces a polymer product with a high isotactic index.
Catalysts that produce isotactic polyolefins are disclosed in copending U.S. patent application Ser. No. 317,089 filed Feb. 28, 1989, and U.S. Pat. Nos. 4,794,096 and 4,975,403. This application and these patents disclosed chiral, stereorigid metallocene catalyst components that are used in the polymerization of olefins to form isotactic polymers and are especially useful in the preparation of a highly isotactic polypropylene.
Catalysts that produce syndiotactic polyolefins are disclosed in U.S. Pat. No. 4,892,851. Many metallocenes consisting of deliberate structural modifications to a syndiospecific catalyst, namely, isopropyl[(cyclopentadienyl)(fluorenyl)]zirconium dichloride, as disclosed in U.S. Pat. No. 4,892,851 (hereinafter referred to as iPr[(Cp)(Flu)]ZrCl.sub.2). The structural modifications have been correlated with polymer properties. Some of the polymer properties which can be very effectively controlled by catalyst structure modifications include molecular weight, melting point and the microstructure. However, all the modifications to the iPr[(Cp)(Flu)]ZrCl.sub.2 have resulted in a decrease in the catalyst efficiency compared to the unsubstituted complex under any given set of polymerization conditions. So far, there have not been any efforts made to use substituent effects for manipulating polymerization efficiencies of the metallocenes.